North Korea’s Asymmetric Submarine Doctrine

While North Korean submarines may be technologically dated, its access denial strategy can still be effective.

By Koh Swee Lean Collin for The Diplomat

July 23, 2014

North Korean leader Kim Jong-Un made headlines last month when he visited the Korean People’s Army Naval Unit 167, part of the Korean People’s Navy (KPN) East Sea Fleet unit based in the South Hamgyong province. Photographs released by the Korean Central News Agency showed Kim on a rusty green-painted submarine No. 748, toying with the periscope in its control room. Kim also reportedly guided an actual drill onboard.

Many foreign analysts used Kim’s visit to comment on the decrepit state of the submarine he was visiting. For example, South Korea’s Defense Ministry spokesman, Kim Min-Seok, remarked that: “It appears that Pyongyang aims to show off its submarine might, but the submarines that our Navy holds are far superior, as ours do not make much noise and it can stay underwater far longer.”

This view is not without merit. From a strictly technical standpoint, submarine No. 748 – a Soviet-era Romeo (or possibly the Chinese Type-033 variant built by North Korean shipyards during the Cold War) – represents a bygone era. The Romeo/Type-033, which displaces 1,800 tons when submerged, traces its roots back to the German World War-vintage U-boat technology that was incrementally improved upon in the 1950s prior to being mass produced by the Soviets. Its combat systems, propulsion and quieting characteristics are considered obsolete by today’s standards.

This stands in stark contrast to the Republic of Korea Navy’s (ROKN) growing stable of modern submarines, including the KSS-1 Chang Bogo and the even more capable KSS-2 Sohn Won-Il, based on the German Type-209/1400 and Type-214 respectively. North Korea’s vessels lack any missile capabilities and can only fire short-range, Cold War-vintage torpedoes. By contrast, ROKN submarines are equipped with the UGM-84C Sub-Harpoon sea-launched anti-ship missiles, which are capable of destroying enemy warships from 60-miles away. They also boast new German-made heavyweight homing torpedoes. The key difference between the two undersea fleets, however, are South Korea’s state-of-the-art combat systems, which are typically comprised of an integrated, digitalized command and control suite, sonar and electronic warfare equipment, as well as quieting features.

Thus, North Korea’s submarine capabilities are a far cry from those of its erstwhile Southern adversary. Moreover, the inter-Korean submarine technological gap will further widen when South Korea’s new submarines, notably the KSS-3, come online soon.

The Rise and Fall of the Korean People’s Navy

The KPN’s golden era was back in the Cold War when it received generous amounts of Soviet military-technical aid. Especially during the 1960s and 1970s, the KPN was arguably one of the strongest navies in the Asia-Pacific region. It was a sizeable force, albeit optimized for coastal patrol and attack duties.

Quantitatively, and in some respects qualitatively, the KPN was superior to the ROKN during the early Cold War when South Korea’s Navy relied mainly on World War-vintage secondhand U.S. equipment. It wasn’t until the early-1980s that the ROKN even inducted its first undersea capability, which were unimpressive Italian-origin mini-submarines. The ROKN’s first full-fledged combat submarine, the Chang Bogo, was inducted only in 1993, almost two decades after the KPN incorporated the Romeo/Type-033 and started to license-build copies of it.

However, as the Soviet Union collapsed and Moscow’s aid to North Korea dried up, the KPN declined precipitously. At the same time, phenomenal economic growth and technological innovations transformed the ROKN into a three-dimensional force, which now stands as one of the most modern navies in the world. Thus, at first glance, the inter-Korean naval balance has increasingly tipped in South Korea’s favor.

Still a Coastal Force

This view is slightly misleading, however. Some view the KPN as a service that seeks to project force over considerable distances. The Romeo/Type-033, for instance, was initially designed as a long-range patrol submarine. Thus, during wartime, many expect it to be used to interdict commerce traveling through South Korean sea lines of communication en route to Busan.

Such a scenario might be attempted if North Korea mounted a major offensive aimed at bringing about Korea’s reunification. Yet, the KPN would be constrained in its ability to project force beyond its immediate waters due to force structural weaknesses and its lack of long-range air cover. This is reflected in its force structure, which in the post-Cold War era has been heavily dominated by small landing craft (including an expanding fleet of assault hovercraft) and coastal combatants. Wartime surface actions would be borne by missile craft and submarines –the KPN’s only offensive capabilities – backed by a handful of light frigates incapable of operating beyond North Korea’s land-based air defense systems.

Only the Romeo/Type-033 is deemed capable of projecting offensive force along South Korea’s coastal flanks. This might have been plausible back in the 1960s and 1970s based on the prevailing state of submarine and anti-submarine warfare (ASW) technologies. Presently and into the future, the non-stealthy Romeo/Type-033 would stand a minimal chance of surviving if it ever ventured beyond air cover, to say nothing of having any tangible success at interdicting enemy shipping.

In light of post-Cold War realities, if Pyongyang’s strategic objective is regime survival instead of forcible reunification, its military posture ought to be seen as strategically defensive in nature. By extension, therefore, the KPN’s wartime missions would be even more tightly circumscribed within its immediate littoral confines. It was already incapable of projecting force further afield during the Cold War, much less so now and into the future.

The Mini-Submarine Menace

Nonetheless, while many focus on the naval technology gap between the two Koreas, other important aspects of the KPN’s development have been neglected. In fact, the North Korean submarine threat doesn’t even originate from the ungainly-looking Soviet-era boats Kim toured recently, but rather from the KPN’s burgeoning fleet of mini-submarines.

For instance, while the ROKN was busy adding a bunch of ultra-modern submarine capabilities, the ROKS Cheonan was allegedly sunk in 2010 by a KPN mini-submarine. Additionally, North Korean mini-submarines have, from time to time, successfully reached South Korean shores undetected.

In the notorious 1996 Geungneung incident, for example, the KPN Sang-O class mini-submarine landed heavily-armed agents ashore in South Korea. According to the sole North Korean survivor’s testimony, the boat managed to evade a sonar-equipped ROKN warship in getting to the coast. Two years later, a KPN Yugo class mini-submarine was caught in South Korean fishing nets and left adrift some 11.5 miles off of Sokcho on the South Korean east coast. However, the captured logbook from the vessel suggested that the boat had managed to land some North Korean agents ashore before disaster befell upon it.

These incidents happened at the same time the KPN’s technical capabilities were said to have atrophied, and the ROKN was rapidly innovating. As this underscores, seeing no hope of “catching up” with South Korea, North Korea has adopted an asymmetric naval doctrine to counter the ROKN’s growing technological strength. Mini-submarines are a key part of this new doctrine.

The Sea Denial Mission

While the KPN may retain its traditional wartime tasks of providing offshore fire support and facilitating coastal amphibious assaults, its primary purpose during wartime would likely be sea denial against any U.S.-ROK amphibious forces. North Korean defense planners remain haunted by General Douglas MacArthur’s surprise landing at Incheon during the Korean War, and are keen to ensure it is not repeated.

Besides carrying out provocations during peacetime, mini-submarines are well-suited for this sea-denial mission. The KPN’s “wolf pack” of mini-submarines are each physically smaller (typically half the length of the Romeo/Type-033), more concealable and possibly more maneuverable within the numerous bays and inlets dotting the North Korean coast. Furthermore, given their simpler technologies and lower costs, the KPN mini-submarines can be produced in much larger quantities than the more complex ROKN boats. Manned by a highly-motivate and well-trained crew that is familiar with the local littoral geography, the KPN mini-submarine fleet would be highly effective using “hit-and-run” tactics against U.S.-ROK amphibious forces.

Indeed, there are a number of signs that suggest that Pyongyang’s mini-submarine program has been at least reasonably successful. For one thing, Iran has acquired the designs and actual samples of the mini-submarines, and deploys its own versions of them to threaten shipping in the strategically-vital Strait of Hormuz.

More notably, the ROKN has recently made a series of recent acquisitions geared towards enhancing its ASW capabilities, and has also held numerous ASW exercises both alone and in conjunction with the U.S. Navy. The recent South Korean live-firing drill near Dokdo/Takeshima Isles was said to be conducted to strengthen ROKN’s defenses against a possible North Korean submarine threat, not long after the North Korean leader’s submarine inspection.

It has been more than four years since the tragic Cheonan incident, yet it is plausible that Pyongyang could have been buoyed by this tactical success to invest even more in its mini-submarine program, which have so far remained largely an enigma. Given its penchant for being highly secretive especially on military affairs, Pyongyang most likely does not publicize its true combat potential.

As such, the international community should not be misled by the recent KCNA pictures, which could have been published to distract from the Supreme Leader’s real wolf pack of mini-submarines. It would be foolhardy to dismiss the latent, asymmetric potential of the KPN.

Koh Swee Lean Collin is associate research fellow at the Institute of Defence and Strategic Studies, a constituent of the S. Rajaratnam School of International Studies, Nanyang Technological University. His research interest encompasses naval affairs in the Asia-Pacific.